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Radeon KMS bug causing wireless crashes, devs please help

Attn: radeon devs, if you're here... thanks for all your hard work.

There's an ongoing bug report on Launchpad, initially directed toward iwl3945, but it appears that the problem is actually with the radeon driver... wireless hangs/crashes during high GPU utilization (like video playback), but only occurs when kernel modesetting is turned on. With KMS off, the hardware runs normally. This seems to be some sort of regression, either in the kernel or in the driver.

Please help... there are lots of folks out there with systems that are unusable unless they manually disable kernel modesetting. I'm one of the affected users, in my case on a Thinkpad T60 with X1400 and Intel wireless. There are also users reporting audio corruption under the same conditions as mentioned above, which disappears when KMS is disabled.

Yes, it would be great if this was looked into. I've got affected hardware as well. Problems with audio (crackling not caused by Pulseaudio) and wireless connection dropping when running with radeon KMS, typically triggered by fullscreen movie playback or in general “GPU load” (for lack of better way to describe it). Both problems disappear when disabling kernel mode setting. Thinkpad Z61m with ATI X1400.

The three last bugs are related to the audio problems I'm seeing when using KMS, two of which I've filed myself.

I've been reluctant to file a bug at freedesktop.org so far, because I don't know if radeon KMS is directly to blame, but what I am sure of is that it triggers the problems. Whether there is some general kernel problem or if KMS alters conditions in a way that shake out bugs in other kernel drivers. So far it looks like only people with ATI IGP or Xnnnn-series cards are affected.

I'm on Ubuntu Lucid x86. Have tested up to mainline kernel 2.6.34-rc7, and the problem persists, so it's not Ubuntu-kernel specific.

(In reply to comment #28)
> Thank you for testing. Appearently, there might be a clash in the PCI device or
> bus configuration. Unfortunately, I'm not expert in this area. It might be a
> good idea to check the PCI device setup using lspci (compare good and bad
> behaviour).

Indeed, the PCI configuration for radeon is different under KMS (bad) compared
to UMS (good):

Also, KMS causes problems for my wireless PCI network controller/driver iwl3945 (drops connection during Flash fullscreen video streaming, when snd-hda-intel crackling is at its worst . So, my system probably has issues out of scope for this bug report, wrt. to KMS. Thank you for all help.

Ha, I just realized Øyvind is the one who posted earlier in this thread. Hi Øyvind! Thanks for the links and the good information, hopefully it will get in front of the right eyeballs with all the linking.

Apparently it's slightly more serious than previously thought... users are reporting full kernel crashes when switching the wifi off using the hardware on/off switch. Disabling radeon KMS causes the behavior to disappear.